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<title>Macro BOOST_CONTRACT_PRECONDITION</title>
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<h2><span class="refentrytitle">Macro BOOST_CONTRACT_PRECONDITION</span></h2>
<p>BOOST_CONTRACT_PRECONDITION — Program preconditions that can be completely disabled at compile-time. </p>
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<h2 xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv-title">Synopsis</h2>
<div xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="refsynopsisdiv"><pre class="synopsis"><span class="comment">// In header: &lt;<a class="link" href="reference.html#header.boost.contract_macro_hpp" title="Header &lt;boost/contract_macro.hpp&gt;">boost/contract_macro.hpp</a>&gt;

</span>BOOST_CONTRACT_PRECONDITION(...)</pre></div>
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<a name="idm45885982920944"></a><h2>Description</h2>
<p><code class="computeroutput">BOOST_CONTRACT_PRECONDITION(f)</code> expands to code equivalent to the following (note that no code is generated when  <code class="computeroutput"><a class="link" href="BOOST_CO_idm45125848583888.html" title="Macro BOOST_CONTRACT_NO_PRECONDITIONS">BOOST_CONTRACT_NO_PRECONDITIONS</a></code> is defined):</p>
<pre class="programlisting"><span class="preprocessor">#ifndef</span> <span class="identifier">BOOST_CONTRACT_NO_PRECONDITIONS</span>
    <span class="special">.</span><span class="identifier">precondition</span><span class="special">(</span><span class="identifier">f</span><span class="special">)</span>
<span class="preprocessor">#endif</span>
</pre>
<p>Where:</p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p><code class="computeroutput"><span class="bold"><strong>f</strong></span></code> is the nullay functor called by this library to check preconditions <code class="computeroutput">f()</code>. Assertions within this functor are usually programmed using  <code class="computeroutput"><a class="link" href="BOOST_CONTRACT_ASSERT.html" title="Macro BOOST_CONTRACT_ASSERT">BOOST_CONTRACT_ASSERT</a></code>, but any exception thrown by a call to this functor indicates a contract assertion failure (and will result in this library calling  <code class="computeroutput"><a class="link" href="boost/contract/precondition_failure.html" title="Function precondition_failure">boost::contract::precondition_failure</a></code>). This functor should capture variables by (constant) value, or better by (constant) reference (to avoid extra copies). (This is a variadic macro parameter so it can contain commas not protected by round parenthesis.)</p></li></ul></div>
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<p><span class="bold"><strong>See Also:</strong></span></p>
<p> <a class="link" href="boost_contract/extras.html#boost_contract.extras.disable_contract_compilation__macro_interface_" title="Disable Contract Compilation (Macro Interface)">
        Disable Contract Compilation</a>,  <a class="link" href="boost_contract/tutorial.html#boost_contract.tutorial.preconditions" title="Preconditions"> Preconditions</a> </p>
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<td align="right"><div class="copyright-footer">Copyright © 2008-2019 Lorenzo Caminiti<p>
        Distributed under the Boost Software License, Version 1.0 (see accompanying
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